Synchronous Belt
Installation and Tensioning
Synchronous belt drives provide many maintenance
advantages that help in your daily struggle to reduce
equipment repairs and hold downtime to the lowest
possible level. Applying the practices provided here will
help to ensure that your synchronous drives consistently
give reliable service and long life with minimal attention.
Installation Check List
1) Disconnect and lock out power source. Observe all safety procedures.
2) Remove belt guard
3) Loosen motor mounts
4) Shorten center distance
5) Remove old belt
6) Inspect belt wear patterns for possible troubleshooting
7) Inspect and clean drive elements-bearings, shafts, etc.
8) Inspect sprockets for wear - replace if necessary
9) Preliminary sprocket alignment
10) Identify proper replacement belt
11) Install new belt
12) Tension belt
13) Final sprocket alignment
14) Replace guard
15) Start drive (look & listen)
16) Re-tension after 24 hours
Safety First
• Be sure to review
and comply with all
building and safety
codes.
• Disconnect and
lockout the power
supply.
• Follow your plant’s
safety rules!
Relieve Belt Tension
After removing the drive
guard, loosen the drive
take-up and move the
sprockets closer together
to facilitate the removal of
the old belt and to ensure
installation of the new belt
without damage.
Inspect Drive Elements
• Inspect and replace faulty
or damaged machine
elements such as worn
bearings or bent shafts
• This not only reduces
the likelihood of future
mechanical trouble, but
ensures maximum service
from the new belt
Clean Drive Elements
• Sprockets should be carefully
cleaned of any rust and foreign
material. A wire brush followed
up with a shop cloth will usually
do the job.
• This is a good time to service
the take-up rails by removing
any rust or dirt, and lubricating
as necessary so tensioning of
the new belt will go smoothly
and easily.
Inspect Sprockets
Sprocket condition and
alignment are vital to belt life
and performance. Never
install new belts without a
thorough inspection of the
sprockets. Look for signs of
wear such as bent or missing
flanges, worn or damaged
sprocket grooves, wobbling
sprockets, cracked bushings,
etc.
Inspect Sprockets
• The easiest way to check sprocket wear
is with a Pi tape. The Pi Tape is graduated
to the nearest 0.001" and the sprocket
can be measured by placing the tape
around the OC of the sprocket. The
Carlisle catalog provides the nominal
sprocket OD. They are the same for RPP
and HTD.
OD tolerances for sprockets:
up to 50mm (1.969"): +0.08/-0.00 mm
(+0.003/-0.000")
>50 to 100 mm (>1.969 to 3.937"):
+0.10/-0.00 (+0.004/-0.000")
>100 to 175 mm (>3.937 to 6.889"):
+0.13/-0.00 (+0.005/-0.000")
>175 mm (>6.889"): +0.15/-0.00 mm
(+0.006/-0.000")
Sprocket and Bushing Installation
Improper sprocket and bushing installation can result in wobble as well
as causing bushings or sprocket hubs to crack and possible shaft
damage. When installing bushings such as QD® or Taper-Lock types,
always follow manufacturer’s instructions.
It is important to never lubricate the tapered surfaces before
installation. Friction is required to achieve the proper clamping force at
recommended bolt torque. Lubrication causes excessive clamping force
which usually results in cracking of the bushings at the bolt hole or
keyway.
Rust, grease and other debris on the shaft and mating surfaces can
make installation difficult and affect torque carrying capacity. Clean
these elements using a fine grit emery cloth and a clean rag.
On flanged bushing types, the flange should never be brought up flush
with the hub face. A small gap between the two surfaces is normal.
When removing bushings, start at the jack-screw hole opposite the
split to avoid cracking the bushing.
Sprocket Installation Procedure
1. Thoroughly inspect the bore of the sprocket and the tapered
surface of the bushing. Any paint, dirt, oil or grease must be removed.
2. Assemble the bushing into the sprocket. Loosely insert the
capscrews into the assembly, but do not lubricate capscrew threads.
(Note: install M thru S bushings so the two extra holes in the hub are
located as far as possible from the bushing’s sawcut).
3. With key in keyseat of shaft, slide sprocket to its desired position
with capscrew heads to the outside. (A few small sprockets may have
to be installed with the capscrews on the inside). If it is hard to slide
the bushing onto the shaft, wedge a screwdriver blade into the sawcut
to overcome the tightness.
4. Line up the assembly so as not to misalign the belts, and tighten
capscrews evenly and progressively. Apply the recommended torque
to the capscrews. There should be 1/8” to ¼”gap between the
sprocket hub and the bushing flange. If the gap is closed the shaft
is seriously undersize.
Sprocket Safety
Maximum Surface Speed
• Synchronous belt drives are
designed to operate at sprocket
surface speeds up to 6500 feet per
minute (33 meters per second).
• Special sprockets are required
for operation in excess of 6500
feet per minute.
• Where vibration is a critical
WARNING: Cast iron products can
safely operate up to a maximum speed
of 6500 feet per minute. For speeds
greater than 6500 feet per minute
ductile iron must be used. Ductile iron
has a safe operating speed up to
10,000 feet per minute.
factor, dynamic balancing of
sprockets is recommended
regardless of the operating speed.
Preliminary Sprocket Alignment
• Use a straightedge or laser tool to make
sure sprockets are aligned correctly
• A string can be used if a straightedge or
laser tool is not available.
• Be sure the shafts of the driver and
driven sprockets are parallel, horizontally
and vertically.
• Be sure the driver and driven sprockets
are in a straight line
• Be sure both sprockets are properly
mounted and as near to the bearings as
practical (to reduce overhung load on the
bearings and shafts).
Sprocket Alignment
Proper Sprocket Alignment
Synchronous belts are much more sensitive to misalignment
than v-belts. Misalignment leads to uneven belt and pulley
wear and premature tensile cord failure. Tracking problems
can also result from drive misalignment.
There are two types of misalignment, parallel and angular.
In parallel misalignment, the driver and driven shafts are
parallel, but the two pulleys lie in different planes. When the
two shafts are not parallel, the drive is angularly misaligned.
Any degree of pulley misalignment will result in some
reduction of belt life. Total misalignment should be less than
1/16” misalignment per foot of drive center distance.
Sprocket Alignment
The straight-edge should make contact at four distinct
points along the outside perimeter of both sprockets.
1
2
There should
be no gaps
between the
sprocket and
straightedge
at 1-2-3-4
3
4
Proper
Parallel
(Off-Set)
Horizontal
Angular
(Pigeon-Toed)
Vertical
Angular
Identify Replacement Belts
High torque synchronous
belts (RPP™ Plus™) are similar
in appearance to Super High
Torque (RPP™ Panther®)
belts. It is important to
identify the correct type of
synchronous belt. To insure
the best performance and
maximum belt life, replace
with the recommended belt.
Installing New Belts
• Place the new belt on the
sprockets. Loosening the
drive take-up in advance
makes this easy.
• DO NOT FORCE the belts
on the sprockets by using a
pry bar or rolling the
sprockets.*
• Do not crimp the belt.*
• Move the sprockets apart
*
Prying or forcing synchronous belts onto the
sprockets can, and usually does, break some of the
load-carrying tensile cords. Crimping will also damage
the tensile cords.
until the belt is seated in the
sprocket grooves, and start
to tighten the drive just until
the slack is taken up.
Apply Tension
The most important factor in the successful operation of a synchronous
belt drive is proper tensioning. To achieve long trouble-free service, belt
tension must be sufficient to overcome tooth jump and to insure proper
meshing with the sprocket. Improper tension is the most common cause
of premature belt failure.
installation
center distance
take-up
Increase the center distance to apply tension
NOTE: RPP Panther belts are constructed to attain proper pitch dimension when
subjected to tension. For this reason, the belt may not fully engage in large
diameter sprockets without applying tension to the belt.
Tensioning Procedure
Method 1: Deflection Force Method
A. Determine the required deflection force range
B. Calculate or measure the free span length
C. Determine the deflection distance
D. Measure the actual deflection force
E. Increase or decrease the actual deflection force
until it is within the required deflection force range
Recommended Tension Tables
8M Panther Ultracord
Recommended Tension Tables
8M Panther Ultracord
Recommended Tension Tables
14M Panther
Ultracord
Recommended Tension Tables
14M Panther Ultracord
Spring Loaded Tensiometer Instructions
1) Measure the span length of the drive. Set the large O-ring at
1/64” for each inch of belt span. For example, set the large o-ring
1/4” for a span length of 16”, at ½” for a span length of 32”, at 1” for
a span length of 64” etc.
2) Set the small O-ring at zero and press down the tensiometer at the
center of the belt span. Depress the tensiometer until the large Oring is even with the bottom of a straight edge placed on the outside
rims of two sprockets.
3) Remove the tensiometer and observe that the small O-ring has
moved from its original setting at zero to the number of pounds
required to deflect the belt to the extent noted above.
Note: For belts wider than
2 inches, it is suggested
that a rigid strip of
keystock or something
similar be placed across
the belt between the point
of force and the belt to
prevent belt distortion.
Electronic Tensioning
Method 2 - Frequency Method
• Another method to assure
precise tensioning works on the
principle of forced vibration
• The Frequency-Finder from
Carlisle measures the frequency of
vibration which is related to the
tension of the belt
Calculation of Belt Natural Frequency
2
T = 0.0104 x K x L x F
2
Where:
T = belt tension in pounds (Lbs)
K = mass of the belt span per inch(lbs/in)
L = length of vibrating span (in)
f = frequency of the belt vibration(Hz)
Drive Engineer
• Tensioning information is
also included in our drive
design software for the
deflection force and
frequency methods
• Drive Engineer may be
downloaded from
www.CarlisleBelts.com
or contact customer service
(866) 773-2926 to order CD
Tensioning Notes
• Should jumping teeth occur, increase the belt
tension until it ceases
• The supporting structure should be checked for
rigidity to make sure the shafts are not deflecting
during periods of peak loading and causing tooth
jump
• Long center distance drives using relatively small
diameter sprockets must provide sufficient tension to
avoid the tension and slack sides of the belt from
intermeshing
Final Sprocket Alignment
Synchronous drives are highly
sensitive to misalignment. The
closer you can come to perfect
alignment, the better. Proper
alignment helps to equalize the
load across the entire belt width,
thereby reducing wear and
extending belt life.
Laser alignment is the most
precise method of alignment and
will aid in eliminating tracking
problems and belt and sprocket
wear resulting from drive
misalignment.
Start Drive
While the drive is running look and listen for any
indications of potential
problems such as excessive
drive noise, misalignment,
sprocket wobble, etc.
Replace Guard
Ensure that the belt will not come
into contact with the guard. Often
just replacing missing bolts in the
guard brackets will remedy this
situation.
NOTE: Effective noise reduction for
power transmission drives can be
accomplished by incorporating a flexible
noise absorbing material with the
protective guard. The guard design
must allow a cooling air passage on the
top and bottom to prevent overheating
the drive.
Re-Tension after 24 hours
When retensioning, it is necessary to use Ts min.
Troubleshooting Synchronous Drives
Normal Failure Mode
The end of the useful life of a synchronous belt is
most often characterized by even tooth fabric wear
and eventually, tooth separation. Any other type of
failure could be an indication that there are other
problems present within the drive.
belt
Troubleshooting Synchronous Drives
Noise
Noise can be an issue with synchronous belt drives. The
noise created by a drive increases with the belt speed. To
minimize noise make sure the drive is aligned and
tensioned properly.
Troubleshooting Synchronous Drives
Sprocket Wear
Sprocket wear can have a great impact on belt wear.
When unusual belt wear occurs, the first step is to
inspect the sprockets. Excessive tooth wear is obvious
with visual inspection. Use a pi tape to evaluate sprocket
wear.
The best sprocket material for minimizing wear is gray
cast or ductile iron. A softer material may wear more
quickly.
Abrasive environments, drive misalignment, and improper
tensioning can lead to rapid belt and sprocket wear.
Troubleshooting Synchronous Drives
Sprocket Misalignment
The leading symptoms of belt misalignment are excessive edge wear (exposing
or fraying the tensile cord), running off the flange, snub breaking (in a stair
step pattern) and excessive drive noise. If sprockets are verified to be in
alignment and problems persist, frame and bearing supports should be
checked for rigidity. The frame may be flexing during operation, causing drive
misalignment.
Proper
Parallel
(Off-Set)
Horizontal
Angular
(Pigeon-Toed)
Vertical
Angular
Troubleshooting Synchronous Drives
Excessive Tension
Excessive tension of a synchronous drive will cause
premature belt failure due to wear and high tooth
stress. The noise level of a synchronous belt drive will
increase considerably if the belt is over-tensioned.
Excessive tension produces fabric wear between the
belt teeth exposing the tensile cord and wearing of the
sprocket teeth. If tooth shear, snub break, or tooth
jump occurs under correct tension, the drive may be
under-designed.
Troubleshooting Synchronous Drives
Under-Tensioning
Under-tensioning is the most common cause of belt
failure. It can cause premature belt wear, tooth
jump and belt failure. Belt wear is characterized by
fabric wear on the tooth flank which can accumulate
material between the teeth. Jumping can cause
tooth shear and tensile cord breakage. Tooth jump
or ratcheting occurs when the belt teeth climb up
and out of the sprocket grooves. The most obvious
indication of tooth jump is a machine gun like
sound. Although there may be no visible evidence of
damage, the capabilities of the belt are likely
destroyed after tooth jump.
Troubleshooting Synchronous Drives
Non-Rigid Frame
A less common cause of belt failure is a non-rigid
frame which allows the center distance to vary when
a load is applied. The supporting structure should
be checked for rigidity to make sure the shafts are
not deflecting during periods of peak loading and
causing tooth jump.
Troubleshooting Synchronous Drives
Overloaded Drive
Severe overload conditions can cause fabric and
sprocket wear on the pressure surfaces, belt tooth
shear, snub break, tooth jump and a resulting
increase in noise level. These conditions generally
force a drive re-design to provide additional
capacity. A wider belt will sometimes accomplish
this.
Troubleshooting Synchronous Drives
Excessive Shock Loads / Start-Up Loads
• Some applications are not conducive to synchronous belt drives
• Use special consideration on drives with excessive or extreme
shock loads or start-up loads - Some drives may require soft start
• Positive drive engagement and the high modulus cord (lowstretch) make synchronous belts less tolerant of severe shock
loads than v-belts which allow slippage
• If you require the characteristics of synchronous belts in a shock
load application, an RPP Panther synchronous belt is your best
choice in these situations
Troubleshooting Environmental Problems
Belt Deterioration
The synchronous belt can deteriorate when operated
in caustic or acidic atmospheres, environments
saturated with vapors from hydrocarbon solvents, and
ambient temperatures above 185°F or less than -30°F.
Specially constructed belts may provide satisfactory
service in a number of applications not suitable for
stock belts.
Troubleshooting Environmental Problems
Excessive Heat
Carlisle standard rubber construction
synchronous belts are compounded for moderate
resistance to heat and should give adequate
service life under normal conditions. The
operating limits of a standard construction
synchronous belt range from a minimum of -32°F
to 200°F ambient temperature (230°F
intermittently). Polyurethane synchronous belts
are only capable of +185°F.
Troubleshooting Environmental Problems
Environments with Excessive Debris
• Synchronous belts should not be used in environments
where excessive debris is present
• Debris can be more damaging to a synchronous belt
drive than to a v-belt drive, which has a tendency to eject
debris from the sheave grooves as the drive operates
• Large debris trapped between a synchronous belt and
pulley will destroy belt tensile cords or drive hardware
• Small debris will become compacted in the pulley
groove, forcing the belt to ride out away from the pulley
and lead to belt failure by destroying the tensile member
Troubleshooting Environmental Problems
Environments with Excessive Debris (cont.)
• Exposure of synchronous belts to oil and other
lubricants should be minimized
• Oil and petroleum distillates may alter the belt polymers
and adhesion systems
• Care must be taken to provide adequate shielding on
drives where debris or contaminants are likely
• Completely enclosing a synchronous belt drive may be
acceptable. Synchronous belts generate less heat than vbelts. Air circulation around the drive is not a critical
consideration except in extremely high temperature
environments.
Synchronous Belt Storage
The quality of a Carlisle Belt is not considered to change
significantly within eight years, when stored properly under
normal conditions. Normal conditions can be defined as
temperature below 85°F and relative humidity of 70% or
less with no exposure to direct sunlight. Beyond eight years,
assuming normal storage, a decrease in service life of
approximately 10% per year can be expected. For belts not
stored under “normal” conditions, the actual reduction in
shelf life is difficult to measure due to lack of precise data
and an infinite number of variables involved. When belts are
stored under abnormal conditions, conservatism is
recommended in estimating shelf life. Improper or
prolonged storage can reduce service life considerably.
Synchronous Belt Storage
Like V-belts, synchronous belts may be stored on pins or
saddles with precautions taken to avoid distortion. However,
belts of this type up to approximately 120 inches are normally
shipped in a “nested” configuration and it is recommended that
the belts be stored in this manner as well. Nests are formed by
laying a belt on its side on a flat surface and placing as many
belts inside the first belt as possible without undue force. When
the nests are tight and are stacked with each rotated 180° from
the one below, they may be stacked without damage.
Belts of this type over approximately 120 inches may be “rolled
up” and tied for shipment. These rolls may be stacked for easy
storage. Care should be taken to avoid small bend radii which
could damage the belts.
www.CarlisleBelts.com
from
www.c-rproducts.com
sales@c-rproducts.com
Tel: +44 1327 701030
Fax: +44 1327 701031